Optimization of ion trapping characteristics for studies of ion photodissociation

Abstract

In order to characterize unambiguously photochemical energy absorption and subsequent intramolecular relaxation dissociation, collision-free conditions are required. Isolated molecule photochemistry may be studied in a quadrupole ion store (QUISTOR) under near collision-free conditions. Photodissociation of primary ions, H2+ and CH4+, has been described and we have reported on the slow multiphoton induced dissociation of protonated dimers of 2-propanol in the infrared region. Ions may be trapped in a QUISTOR in either a total storage mode wherein ions of different masses are stored simultaneously, or a mass selective mode wherein single ion species are isolated. Utilization of the QUISTOR as an ion/molecule reactor in the total ion storage mode facilitates the formation of secondary ions chosen for study, their isolation, and irradiation. Determination of the ranges of ion masses which may be stored in each mode is described. In the total storage mode, ion mass-to-charge ratios to m/e 455 have been observed. Selective storage to m/e 219 is reported, though with poor resolution. The effects of variation in trapping parameters including drive frequency and physical dimensions of the device are discussed.